Links using UID is a great feature. Plone store "resolveuid/YOURUID" as the path to the object. So you can change the path of this object without updating all your content which use it.
When rendering happens Plone transform theses to real path / URL.
Even if the transform do not happens, URL with resolveuid will work in browser because there is a view or PythonScript which do the redirect.
So if your image do not show up it can be:
- because you have deleted it
- because your current location is weird.
- there is a bug